Congenital hydronephrosis is the most commonly found abnormality on antenatal ultrasound. Hydronephrosis, however, may represent dilation without significant obstruction and the distinction between these two conditions may decide for or against surgical intervention. Current patient management involves a combination of X-ray and nuclear medicine studies. These studies provide limited morphological information, involve significant radiation exposure, and are not always conclusive in establishing the risk of future renal deterioration. MRI offers a non-invasive method for evaluating anatomy in a high-resolution format and potential specific information regarding renal function (blood flow, filtration, and excretion parameters). Methods During the past year, we successfully developed several novel fluoroscopy MR imaging techniques ato measure renal function in animal models and in pediatric patients. In our first animal model, MR images showed precise delineation of the hydronephrotic pelvis and corticomedullary junction, and dynamic Gd-DTPA studies differentiated obstructed kidneys. In a second animal model, we validated the MR blood flow measurements using microspheres, and improved the accuracy of the data using a newly developed double echo imaging technique. By using the dual echo pulse sequence, we were able to calculate improved estimates of relative bloOd flow and kidney filtration rates. We performed preliminary MR studies of 10 pediatric patients to evaluate our imaging capabilities. These patients had a variety of urological abnormalities, including duplication collecting system (2), congenital left renal artery stenosis (1), and urinary reflux (4). Each study consisted of a set of standard MRI sequences employed in routine clinical evaluation and bolus injection of a MR contrast agent. Discussion Initial studies clearly demonstrate that dynamic MRI can provide valuable clinical information for the evaluation of pediatric patients. The combination of both detailed anatomic and functional information in a single study cannot currently be matched by any other imaging modality.